[regexp] Support unicode capture names in non-unicode patterns

test/mjsunit/harmony/regexp-named-captures.js

Index: test/mjsunit/harmony/regexp-named-captures.js
diff --git a/test/mjsunit/harmony/regexp-named-captures.js b/test/mjsunit/harmony/regexp-named-captures.js
index 9d6b9a95c7e0909e0cee0e27730e09c6be4d6520..22565ef6bb382b4bf710d61273ed9bb4421c6e0e 100644
--- a/test/mjsunit/harmony/regexp-named-captures.js
+++ b/test/mjsunit/harmony/regexp-named-captures.js
@@ -147,7 +147,7 @@ assertThrows('/(?<𐒤>a)/u', SyntaxError);  // ID_Continue but not ID_Start.
 assertEquals("a", /(?<π>a)/.exec("bab").groups.π);
 assertEquals("a", /(?<$>a)/.exec("bab").groups.$);
 assertEquals("a", /(?<_>a)/.exec("bab").groups._);
-assertThrows("/(?<$𐒤>a)/", SyntaxError);
+assertEquals("a", /(?<$𐒤>a)/.exec("bab").groups.$𐒤);
 assertEquals("a", /(?<ಠ_ಠ>a)/.exec("bab").groups.ಠ_ಠ);
 assertThrows('/(?<❤>a)/', SyntaxError);
 assertThrows('/(?<𐒤>a)/', SyntaxError);  // ID_Continue but not ID_Start.